Upgrading Graphics Card

Chances are, you'll need a low profile bracket (kind of unusual for dual slot GPU's to include), though with skill, and a pack of brackets from Newegg for $10, and a whole lot of luck, it may 'physically' fit. 

Still, you'll have to contend with the PSU, which on that desktop, even if mid tower & no bracket alteration required, you'll need to upgrade the PSU, it may or may not have either the one or two required 6 pin power connectors, plus at 305W, isn't going to work anyway. 

I suggest that you look for a XPS 8700 on promo, it's not the latest, though there are still many new, still sealed in the box, marked down to move. Plus will get at least a quad core i5 CPU, which will be needed to help the GPU run better (no bottlenecks), and probably more RAM also. It's also a good chance that an i7-4770 ot 4790 is installed, which would be even more powerful. I purchased mine shortly after release at Costco for $699.99 plus tax & shipping, the very same configuration was on the Dell site for $350 more, or $1,049.99. (plus tax & shipping). Have since upgraded the RAM, GPU, and CPU, so is quite upgradable & you should be able to secure one at a great price. 

Just make double sure it's New, and not 'open box' or 'refurbished', as you'd be purchasing someone else's troubles, it would be better to grab a XPS 8900 on promo than that. Yet the XPS 8700 should be on promo on many reputable sties (clearance). Just don't purchase from Best Buy, they'll charge full price if given the chance, and stick you with an i5 rather than i7. I found it kind of odd that Best Buy was charging $50 more for the XPS 8700 with i5, 8GB RAM (one stick only), and some AMD DDR3 GPU, than I paid for my fairly loaded model at Costco. 

While the XPS 8700 isn't the very top of the line PC, it's a great mid level choice that should last for years. And yes, it has a 460W PSU, plus two 6 pin GPU connectors. I don't know what to tell you if it has an 8 pin connection, though there are decent upgrades for the XPS 8700, up to some of the nVidia GTX 970 models, and I suspect the GeForce 1070 will be an approved model, since it's supposed to be easy of the wattage. Right now, nVidia has a better outlook, and lots of support out of the box for Dell PC's. 

Also, by default, the XPS 8700 doesn't ship with Windows 10 at 3rd party retailers, usually Windows 8, 8.1 or 7 Pro. If purchased from Dell, it may ship with W10, though if it were me, I'd get on Chat & insist on 10 Pro for the price & be emailed the proof of offer. Though it may show in the summary at checkout, it never hurts to try & upgrade software from Home to Pro, helped a relative get 8.1 Pro, when all that was offered at the time was 8.1 Home. By the time I was through on the chat, 8.1 Pro was in the cart as a bonus (charged for, then subtracted). Plus got a discount on 16GB RAM, rather than the odd 12GB configuration for a notebook (a 8GB module combined with a 4GB one), even the OEM's recommends against this practice, so why do they do it anyway. 

By chance, my XPS 8700 shipped with two 4GB modules & two 2GB ones, of different brands (Samsung & Hynix)! 

Whatever, don't bother with the drivers on any included DVD, download GeForce Experience (if nVidia) & it'll sense & download/install the latest drivers for the installed OS. AMD has their own updating software, a small app to be downloaded to detect the GPU, and will then after you agree, download & install the proper drivers for your OS. When given the choice, unless you're into gaming, you can just install the audio & graphics drivers, sometimes a bunch of junk not needed is installed by default. 

Good Luck!:emotion-2: